The short answer is that sencha touch technology does not support responsive design out of the box as most people think of it.

You can specify size constraints, and a few position via JavaScript to the layout managers, but the reality is that it's not "true responsive" as one might think of it as it pertains to CSS media queries controlling how things are positioned and sized on screen.

If you want to achieve this, you're going to have to put in the sizing, positing information into CSS and have that drive the look and feel of your app, rather than putting that information into the components themselves.